This invention concerns lip rolling or curling machines, which are widely used for forming a lip on the rim of thermoformed plastic containers, such as disposable cups, food packages, etc. The basic design for these machines has remained unchanged for many years, and is described in U.S. Pat. No. 3,337,919 issued on Aug. 29, 1967 for a "Container Rim Bending Apparatus". In this machine a train of nested cups or other containers is fed into a transition conveyor, which feeds the cups into the circular space between a set of rotating feed rollers, which rollers engage the cup rims and rotate the cup stack. A slight tilt of the rollers out of a radial plane causes the cups to also be advanced into the machine at a speed corresponding to the rate of roller rotation and the degree of tilt of the feed rollers.
The cups are thereby advanced into the interior of a heating oven, confined within a set of three guide rods as the cups are advanced through the oven. After exiting the oven, the train of nested cups is directed into a circular space between a set of rotating curling screws, which engage the heated rims of the cups and progressively form the same to create a lip on the rim of each cup, a helical groove on each curling screw collectively carrying out the forming process as each cup is advanced by the groove engagement past the curling screws.
While this basic design is quite effective and has been widely and successfully used for many years, each of these components as heretofore produced has significant drawbacks, particularly for machines which are adjustable to accommodate different cup sizes and shapes.
In copending applications U.S. Ser. No. 09/203,897 filed on Dec. 2, 1998 Attorney Docket No. BON-111 and U.S. Ser. No. 09/203,896 filed on Dec. 2, 1998 Attorney Docket No. BON-111-1, there is described and claimed improved feed roller and curling screw mechanisms respectively, which renders adjustments thereof much quicker and easier, as well as avoiding shifting of the center point of the spacing between the rollers and screws respectively.
A significant disadvantage of prior heating oven mountings is that the oven cannot easily be removed for servicing, or to access other components for adjustments or servicing. Sometimes, a lengthy delay is involved while waiting for the oven to cool sufficiently to work on parts of the machine close to the oven.
The guide rod set which extends through the oven and guides the containers must likewise be adjusted to each cup size, and heretofore each rod in the set was adjusted separately. This inevitably resulting in misalignment of the center axis of the guide rod with the circular space between the feed rollers and/or the curling screws, which misalignment in turn limited the rate at which the cups could be processed by the machine.
Also, the effect of a given adjustment could not be determined until the machine was restarted, since it must be stopped during the making of adjustments, greatly increasing the time adjustment needed for making a set up.
The transition conveyors previously used suffered from some of the same disadvantages, i.e., accurate alignment with the center axes of the feed rollers was not maintained during adjustments, and/or adjustments affected the tensioning of a feed belt, requiring additional separate steps to retension the drive belt.
Accordingly, an object of the present invention is to provide an improved oven mounting for lip rolling machines which greatly facilitates access to the machine for service and adjustment, and for removal of the oven for servicing.
Another object is to provide an improved adjustment mechanism for the guide rod set carried within the oven which renders adjustments quicker and easier while maintaining accurate alignment with the other machine components.
It is yet another object to provide an improved transition conveyor which is easy and quick to adjust for different cup sizes while maintaining accurate alignment, and is removable for easy servicing.